A known accelerator apparatus controls an acceleration state of a vehicle according to the amount of depression of an accelerator pedal, which is depressed by a foot of a driver of the vehicle. In the accelerator apparatus, a rotational angle of a shaft, which corresponds to a rotational angle of a pedal arm connected to the pedal, is sensed. In the vehicle, an opening degree of a throttle valve, which adjusts a quantity of intake air drawn into cylinders of an internal combustion engine of the vehicle, is determined based on the sensed rotational angle. JP2007-253869A discloses an accelerator pedal apparatus that includes a spring (an urging means) and a hysteresis mechanism accommodated in a supporting member that rotatably supports the shaft. The spring urges the shaft in an accelerator closing direction to rotate the shaft in the accelerator closing direction. The hysteresis mechanism makes a pedal force, which is applied to the accelerator pedal at the time of depressing the accelerator pedal, to be larger than a pedal force, which is applied to the accelerator pedal at the time of releasing the depressed accelerator pedal.
However, in the accelerator apparatus of JP2007-253869A, the supporting member has an opening, which corresponds to a movable range of the pedal arm. A foreign object (e.g., a small pebble, particulate debris) may possibly enter an interior of the supporting member through this opening. When the foreign object enters the interior of the supporting member, the accelerator apparatus may not function properly.